As for "planting" the pinky, it seems to me some folks equate planting to super gluing your finger to the top of the mandolin, unable to move it if you wish to play closer or further from the bridge. I'm curious as to why that would be a problem. I can't speak for others, but my pinky moves when I move my hand, probably because the two are attached. Curiously, I'm able to plant my pinky or unplant it at will, depending on what I'm playing. And I'm not even very good. Surely this is not a problem for good players.
As for concerns about damage to the finish by planting or brushing your pinky on the top, that is what pick guards (i.e., finger rests) and made for ain't it? In my own preference, though I don't mind an instrument that looks played, though Monroe's is a bit excessive IMO. I cover the surface of both my mandos with thin, clear plastic to keep my fingernail from scratching it. Cheap, easily removed and works and looks good.